Development of a durability classification system for protective coatings for concrete

Anti-carbonation coatings for concrete act as barriers to carbon dioxide and thus prevent carbonation. They are extensively used in the rehabilitation of concrete structures throughout the world to prolong the service life of a structure. This paper describes a project, which aims to evaluate the performance of coatings after natural and artificial weathering. Test methods currently available in draft and current CEN Standards (crack bridging, water vapour resistance, CO2 diffusion resistance and liquid water resistance) will be used. The duration of the programme will be five years for natural weathering and a minimum of 2500 hours QUV exposure for artificial weathering. The project started in April 1997 and should be completed in March 2003. Ten different coating systems have been applied to different strength concrete beams, mortar specimens and unglazed ceramic tiles. Urban and marine sites are being used to naturally weather the specimens. The coatings will be monitored during the period of weathering to investigate changes in the physical properties of the coating. From this information a classification system will be evolved to guide the specifier in the selection of a coating to suit their purpose. The work will also be used to validate European Standard tests and classification systems currently being drafted. This paper summarises the work to-date and background information on the project.